Abstract

A granite body in northern New Brunswick, cropping out at the epicenter of a recent sizable earthquake, has a distinctive assemblage of microstructures. Optical and transmission electron microscopy demonstrate a sequence of microstructural development from ductile through transitional into brittle regimes. Overprinting relationships of later (transitional to brittle) features are due to periodic formation of extensive microfracture arrays that are healed by mineral precipitation from circulating pore fluids and therefore are able to be fractured at a later time. These structures are possible paleoseismic indicators.

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